1. Field of the Invention
This invention pertains to coaxial jacks. More particularly, this invention pertains to a switching coaxial jack which is suitable for use in high frequency transmission rate applications.
2. Description of the Prior Art
Switching coaxial jacks are well known. An example of such is shown in U. S. Pat. Nos. 4,749,968 and 5,467,062 both to Burroughs. Another example is shown in U.S. Pat. No. 5,246,378 to Seiceanu.
Prior art switching coaxial jacks included two generally solid center conductors disposed in parallel alignment in a grounded electrically conductive housing. A switching assembly is positioned between the two center conductors.
The switching assembly includes a V-shaped spring with a first end biased against a first of the center conductors and with a second end biased against a second of the center conductors. As a result, the center conductors are in normal signal flow communication such that an electrical signal on one of the center conductors passes through the switching assembly to the other center conductor.
Such switching coaxial jacks would commonly be used in the telecommunications or video transmission industries. A rear end of the housing is provided with connectors for semi-permanent or permanent connection to coaxial cables. The front end of the center conductors are provided with jack ports for receiving a plug of predetermined dimensions. Normally, such switching jacks are operated without plugs inserted within the ports. Accordingly, a signal entering a center conductor from one of the rear connectors passes through the switching assembly and is transmitted out of the jack device through the other rear coaxial connector.
From time to time it is desirable to access the jack in order to re-route the signal or to input a new signal. To accomplish this, a jack plug with attached coaxial cable is inserted into one of the forward ports. Upon insertion of the jack plug into the forward port, the jack plug engages the V-shaped spring causing it to be moved away from the center conductor associated with the port into which the plug is inserted. By causing the V-shaped spring to be moved away from the center conductor, the center conductor is no longer connected to the other center conductor such that the signal passes directly along the entire length of the center conductor and out the port. In addition to breaking the connection between the two center conductors of the jack, insertion of the plug also causes the other center conductor to be electrically connected to ground across a resistance so that the desired electrical impedance of the system is maintained.
With the structure thus described, normal signal flow from rear connector to rear connector passes through the V-shaped spring. There is a substantial length of the center conductors which extend beyond the V-shaped spring without connection to any ground or other source of connection. In the past, these free lengths of center conductors typically presented little or no problem in the telecommunications industry. However, with progressively higher transmission frequencies, the free lengths of center conductors can present distortions to signals or otherwise impair signal integrity.
Another problem associated with prior art switching coaxial jacks is admission of dust or other contaminants to the switching assembly. Such jacks typically have free airflow through the forward ports into the switching assembly of the jack.